Scientists recently have developed a lunar rover that can produce solar cells out of lunar dust by getting Silicium out of it - i initiated a thread about it.

As far as I know that dust is Siliciumdioxyde.

Doesn't all this together mean that the rover gets the oxygen out of the dust too? If yes what then is the reason that NASA wants a technology to get oxygen out of lunar dust? Is Regolith a mixture of several different dusts containing oxygen?

Well,
Lunar soil (regolith) contains SiO2, which (at a guess) gets reduced to pure Si and laid down to make the solar panels. However, Si02 is apparently neither the most plentiful nor the most easily processed source of lunar O2. That is apparently Ilmenite, IIRC FeTi03. Going by what I've read, separating and reducing that is a lot easier than separating and reducing the SiO2. Basic ilmenite processing can apparently be done by heating it to about 900 degrees in the presence of hydrogen (which you have to ship in). After that you cool and separate the gasses, cracking the produced water to recover the hydrogen and oxygen. The big plus to this is that you can do the heating (the most energy intensive part) with a solar furnace. Processing the remaining metallic crud into iron, titanium and more oxygen is possible but beyond the scope of this post.

Alex Freundlich, research professor of physics, and Charles Horton, senior research scientist at the Texas Center for Superconductivity and Advanced Materials at UH, or TcSAM, are developing methods to manufacture huge solar cell arrays on the moon using materials from the lunar soil

then all they plan to do is

Quote:

use an autonomous lunar rover to move across the moon's surface, to melt the regolith into a very thin film of glass and then to deposit thin film solar cells on that lunar glass substrate.

Nothing here suggests to me the extraction of oxygen, even as a byproduct. They don't have any technology developed yet. At this point they are just studying chemistry.

The focus of my question has two focusses - if there would be a rover using lunar Silicium for solar cells then the rover must have broken up Siliciumdioxyde. The german article said that the rover really will do that - then the rover would get oxygen too. In that case the production of oxygen is mangaed one way already and now an additional way would be looked for.

But - as I said in the other way a few moments ago the german article is incomplete obviously.

- if there would be a rover using lunar Silicium for solar cells then the rover must have broken up Siliciumdioxyde. The german article said that the rover really will do that - then the rover would get oxygen too.

Just because the rover would get silicon from silicondioxide does not automatically mean that you get silicon and pure oxygen. Probably you would get pure silicon some other oxygen compound, like titanium oxide or something like that. Naturally it would depend on the exact chemical reaction used.

Quite correct - my point is that during the process of getting pure Silicium there necessarily will be oxygen freed out of the SiO2. It depends on the process and the other elements and chemicals involved if the oxygen remains free or is going to be bound into other molecules during the process. In this last case there will be no free oxygen after the process terminated.

But essential is that during the process there will be free oxygen necessarily - may be for shortest time only. This detail I am focussing on in my previous post.

There may be several alternatives how to design the process.

As I said in the other thread about solar cells producing rover the german article I referred to was incomplete. I will have to have a second look into the New Scientist's article to verify something more detailed regarding those alternatives.

An article under www.wissenschaft.de is reporting details today other threads of the Technology could refer to also.

The article says that Eric Cardiff, Goddard Space Flight Center, has been using Vacuum-Pyrolysis in a/the simulation. Sunlight has been focussed onto lunar regolith heating the regolith to 2,500Â°C. 20% of free oxygen have been got.

Advantages - according to Cardiff - :

1. no materials from Earth required.
2. it is not required to lok or search for a particular mineral.

The remnants could be used for lunar roads, radiation shielding or buiÃ¶ld something else (according to Cardiff). Cradiff is supposing that the temperatures required could be significantly reduced if the air pressure is reduced by another factor of 1,000.

Another team around Mark Berggren,Pioneer Astronautics, Colorado, apllies carbonmonoxide to the lunar dust.

Yet another team at Pratt & Whitney Rocketdyne applies a method called Magma-Electrolysis. The lunar dust is melted and then the oxygen is freed by using a current.

The article unfortunately doesn't list a link to no journal etc.

But it lists a number of elements left after the oxygen is freed:

Silicium
Calcium
Magnesium
Iron

(Might Magnesium be interesting as part of propellants? I remeber having read under www.bernd-leitenberger.de that there is a propellant at least based on Magnesium.)

John Wickman has talked about using Lunar soil derived aluminum powder/LOX mixtures as a rocket fuel. Given the chance, aluminum particles form a tenacious oxide layer which reduces their reactivity in oxygen. This is why such a propellant might be viable, the risk is that aluminum/LOX can behave as a very powerful explosive. Magnesium particles also form oxides at their surface, but the general mismatch of the crystalline lattices of the metal and the oxide in this case means that the the oxide does not adhere at all well to the metal surface and the magnesium remains very reactive. This contributes to magnesium/LOX mixtures being friction sensitive, burning with equivalent particle size is also much more rapid. It might be possible to coat magnesium particles in something protective at cryogenic temperatures, but even were that successful it would increase the chamber volume required for complete burning.

John Wickman has also talked about pressurizing Aluminum/LOX mixtures through a tubopump, this would result in some of the aluminum oxide being worn away and sounds very risky.

There are of course more possibilities if you bring some propellant from Earth, for example you could mix metal powders in with a liquid fuel and burn it in LOX. Hybrids would also be possible, but they aren't that well suited to high performance.

Consider an Aluminum fueled hybrid with (Lunar Produced) LOX oxidizer. The fuel grain could be either sintered Aluminum particles (tolerating and possibly improved by the presence of glass, Aluminum Oxide and other metallic particles). Glassy binders could reduce thermal conductivity and facilitate the release of Aluminum into the flame zone. A small amount of hydrocarbon binder could serve similarly, but would probably need to be brought from earth. It might, alternatively, be produced from wastes, probably reduced to a â€œcharâ€

I like the hybrid aluminum/LOX motor idea. It can be fueled with 100% lunar material. Of course the engineering details are the make or break issue. Rocket science is easy, but rocket engineering is not. Anybody want to make such an engine on Earth to show it can be done?

Iron can also be used as a fuel. There was some talk some time ago about using it to power cars, But as far as I know no development work has been done outside universities. Similarly it could - in theory at least. be used in rockets.

The problem with a lot of these things is that you can develop a process to extract what ever mineral/gas you want out of the lunar regolith. (providing it's there in the first place.)
That's the way chemists have always done things. You want A you design a process specifically to get A.
It seems to me that no one has ever designed a generalised solution to the problems of chemistry.
A small system of reactors/furnaces that will seperate any and all the compounds and elements in a pile of dirt/regolith.
Something like that is urgently needed for lunar/mars exploration. We don't need just oxygen or just silicon or just iron.
We need everything. Especially at the beginning.
The list of trace elements you need to grow something hydroponically is quite long. Miss one element and your seeds won't grow.
You want to build anything useful you don't need just iron or just aluminium or just titanium.
You need ceramics, semiconductors. acids, U name it. Practically the whole periodic table.

So ir would be really neat if the first explorers/settlers has a generalised chemical factory with them. Shovel in regolith at one end, and out pops all your neatly packaged elements at the other.
Such a generalised factory would be highly inefficient compared to normal chemistry. A chemist trying to recover chemical A designs a process that is highly efficient. Everything, apart from chemical A is considered waste and is discarded. If the waste is to be processed to recover chemical B then that is somebody elses problem, and so on.
But in a new lunar environment where you have nothing to start with and you need everything then a way to process the regolith - really process it - into all it's elements is, I think, a high priority.
Now I don't think that this is something that would be intrinsically difficult to do, after all the chemistry of separating compounds is well known. But someone needs to sit down and design the system. build it into a small robust module and sell it to NASA before they get to the moon and start to think
"Wouldn't it be nice...".

Since iron is a heavier atom it would have a lower ISP. Aluminum is much more efficient as a fuel. Not as good as hydrogen or methane or even kerosene, but better than iron.

Frediiiie wrote:

the whole periodic table

Worse than that. There are only 92 (natural) elements, but we need COMPOUNDS. We simply do not know how to make any random compound given only elements as a starting material. If we did know how to do that, we could make gasoline or insulin or most organic compounds out of just air.

What constitutes a resource depends on circumstances. The relatively thin deposits of ironstone, limestone and coal, right on top of each other, at Coalbrookdale, were an ideal resource for the start of the Industrial Revolution, but would be laughable as resources today. So the ISRU we do to get a toe-hold in space will bear little relation to that which we do to sustain a massive human presence. It probably won't be comprehensive for some time. We will do as much as we can with rock, glass and native iron. Possibly one of the first products of a lunar chemical industry would be organosilicon compounts; they perform well in space as lubricants and rubbers, and the simplest are 70% silicon and oxygen by weight.

The first products will DEFINITELY be propellants. A rocket is about 90% propellant, and the other 10% can be brought from Earth! If the rocket is reusable, then only spare parts need to be brought from Earth, which would be, what, 1% of all the mass needed to be moved? So with only propellants on the Moon our transportation gets 99% more efficient right there.